Device at presses for dewatering paper and pulp webs



B. A. LUNDIN Sept. 15, 1970 DEVICE AT PRESSES FOR DEWATERING PAPER AND PULP WEBS 3 Sheets$heet 1 Filed May 22, 1967 INVENTOR Sept. 15, 1970 B. A. LUNDIN 3,528,883

DEVICE AT PRESSES FOR DEWATERING PAPER AND PULP WEBS Filed May 22, 196' 3 Sheets-Sheet 2 Sept. 15, 1970 B. A. LUNDlN 3,528,883

DEVICE AT PRESSES FOR DEWATERING PAPER AND PULP WEBS Filed May 22, 196' 3 Sheets-Sheet 5 United States Patent 3,528,883 DEVICE AT PRESSES FOR DEWATERING PAPER AND PULP WEBS Btirje Arvid Lundin, Halmstad, Sweden, assignor to Nordiska Maskinfilt Aktiebolaget, Halmstad, Sweden, a corporation of Sweden Filed May 22, 1967, Ser. No. 640,091

Claims priority, application Sweden, June 6, 1966,

7,722/ 66 Int. Cl. D21f 3/08 US. Cl. 162-358 8 Claims ABSTRACT OF THE DISCLGSURE The present invention relates to a press for dewatering a humid or a wet fibre web, this press being of the kind having an upper presser roller and a lower driving roller and between them a smaller presser roller and the purpose of the invention is to provide a more even pressure which has been achieved by letting an endless, porous (open) wire of cloth which is difficult to compress, run over the small presser roller and through the press nip between the upper presser roller and the smaller presser roller and under tension about the smaller presser roller, the latter then serving as a pulley for said wire or cloth.

The present invention has reference to presses for dewatering wet or humid webs, e.g. a paper web or another fibre web carried by a felt, of the kind comprising two rollers situated one above the other and running in the same directions, viz. one presser roller and one driver roller situated therebelow, said driver roller adapted, via a presser roller of a considerably smaller diameter and situated between and parallel to said two rollers and an endless, porous (open) cloth which is difficult to compress, to transfer a driving moment to the upper presser roller. So as to reduce the hydraulic pressure in the press nip the small roller is, according to a known embodiment, provided with peripheral circumferentially extending grooves. It is carried on rods only at the ends. For the reason that the diameter of the last mentioned roller is small, the press nip will be short which means that the specific pressure (the surface pressure) will be high for a given line pressure. An essential advantage obtained by the use of such a small presser roller between the two big presser rollers is to be seen therein that the grooves on the roller quickly leave the contact with the felt which results in a very small rewetting of the same. On the other hand, due to the grooves there occurs often a remarkable marking of the fibre web. Due to the rather small cross dimensions of the small presser rollerits diameter will normally be only 5075 millimeters-and its considerable length which as a rule amounts to -7 meters and due to the fact that the roller is carried only at its ends it will due to the pressure form the larger rollers be bent in an outwardly directed bow. The abutment or contact of the small pressure wall against the larger rollers will for this reason not be uniform which has a detrimental influence of the dewatering. Another drawback in the known press is to be seen therein that both of the larger rollers have to be driven for the reason that the small roller cannot transmit the actual drive moment.

The purpose of the present invention is to eliminate the drawbacks of the above described press type. The main feature of the invention is to be seen therein that the cloth which as has been described in the aforegoing, is difficult to compress runs on the small presser roller through the press nip between the latter and the upper presser roller and is adapted to be moved under tension around the small presser roller which also serves as a 3,528,883 Patented Sept. 15, 1970 pulley for the cloth. Due to this cloth which is arranged in the way described and which may comprise a com monly known Fourdrinier felt, the small roller is kept straight during its operation between the two large rollers. The cloth also ensures that the fibre web be not marked. The hydraulic pressure will also be very low in a wire (cloth) which considerably facilitates the dewatering of the paper web. Due to the small cross section of the small roller any rotable degree of rewetting of the felt is prevented for the reason that the felt immediately after the press nip leaves the cloth about the small roller. The cloth may also transfer considerable drive moments in such a way that only one of the large rollers has to be driven, viz. the lower one. Thus, the drawbacks in the known press are eliminated by means of the invention and at the same time the advantages of the same are preserved with regard to a good dewatering and in certain cases the dewatering is further increased.

In the following the invention will be elucidated with reference to the accompanying, essentially diagrammatical drawings. In the drawings:

FIGS. 1 and 2 are end views of two different embodiments of the invention,

FIG. 3 shows, on an enlarged scale, a completing end elevation of the embodiment shown in FIG. 1, and

FIGS. 4 and 5 illustrate two further modifications.

The upper roller of the press, the larger presser roller, has been denoted by reference numeral 1, its lower roller, the driving roller has been denoted with reference numeral 2, and the smaller intermediate presser roller by reference numeral 3. A wire or cloth 4 runs over the small roller and encloses the same with an angle of more than 180. The cloth 4 encloses with an angle a, which in the shown embodiment exceeds also the driving roller 2 which is supposed to be driven directly. The cloth 4 runs further over an expansion roller 5, a tension roller 6 and an adjustment roller 7. The cloth further runs past a suction or exhaust box 8 by means of which, water brought along is removed from the cloth. A scraper 9 abuts against the lower roller 2 for removing water from the mantle of this roller. Reference numeral 10 denotes a machine felt passing through the press nip 11 between the upper presser roller 1 and the small presser roller 3, this machine felt carrying a fibre web 12 to be dewatered. After the press nip 11, the fibre Web 12 is guided by a roller 11 away from the felt 10.

In the press nip 11 the water in the fibre web 12 is transmitted via the felt 10 to the cloth 4 from which the water is removed through the box 8. The tension in the cloth 4 maintains the roller 3 straight in spite of the considerable side pressure acting on it by means of the larger rollers 1, 2. For collecting water that may be sprayed at both sides of the press nip 11 there are arranged screens 14 and 15.

The embodiment shown in FIG. 2 corresponds to the one shown in FIG. 1 with exception of the fact that the small roller 3 according to FIG. 2 has been arranged on the left hand side of the connection line 16 between the longitudinal axes of the two larger rollers 1 and 2.

In FIG. 3 there is shown a bearing device suitable for the roller 3. As obvious from the embodiment shown in this figure, the shaft 17 of the small roller 3 is at both ends (only one shown) carried for rotation in a bearing 18 having a transversal sleeve 19 which is displaceable on a rod 20 with one end journalled in a stationary bracket 21. By means of adjustment and locking nuts 22, 23 which can be screwed on the free threaded ends 24 of the rods 21, the shaft 17 can be moved closer to or away from the connection line 16 between the longitudinal axes of the rollers 1 and 2 whereby the pressure in the press nip 11 is increased or reduced, respectively.

Reference numerals 14 and 15 denotes screens for collecting sprayed water.

In the embodiment shown in FIG. 4 the upper presser roller 1 has been replaced by two smaller presser rollers 1', situated one after the other. Between the driving roller 2 and each one of the smaller upper rollers 1' there is journalled a small presser roller 3. There runs over each roller 3 a felt sieve 4 essentially in the way described. The cloths also enclose a considerable part of the driving roller 2. There is between the rollers 3' arranged a suction box 25 for dewatering the felt 10 passing through the press after the first press nip 11'. So as to prevent water, spraying from the press nip 11', to enter the press nip 11" it is advisable to arrange a rubber edging 26 on the under side of the suction box 25. The fibre web 12 may be removed from the felt 10 immediately after the first press nip 11 by being passed over a pulley 27. Thus, when the fibre web 12 together with the felt 10 enters the press nip 11" between the next pair of preser rollers 1' and 3', the felt has, through the suction box 25, lost a great deal of its water contents and the dewatering of the fibre web 12 in the second press nip 11" will for this reason he very good.

Instead of using, as shown in FIG. 4, two felt wire cloths, viz. one for enclosing each one of the rollers 3, one may as shown in FIG. be satisfied with one single cloth 4'. This single cloth 4' extends, after being laid about the first roller 3, practically about the whole of the driving roller 2 and runs thereupon over the second roller 3. As is common, a number rollers 5, 6 serve for adjustment and tensioning of the cloth 4'.

As a dewater cloth 4 there is used one which is porous and difficult to compress. There is as a rule used a common Fourdrenier wire either of metal or synthetic fibres. If last mentioned material is used, there is advisable to use monofilament yarns for the warp. The mesh size of the wire or cloth should not exceed 1 millimeter.

The invention has been described in the aforegoing for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims. Thus, the difierent portions of the press may be constructively modified in many ways within the scope of the appended claims. This is true in particular for the carrying of the small presser roller 3 at its ends and the device for increasing and decreasing the pressure in the press nip. Even though, due to the use of a wire or cloth which encloses not only the small roller 3 but also a large portion of the driving roller 2 as indicated in the aforegoing, it is suitable to drive the lower roller which in turn drives the cloth 4 and the small roller 3 and the latter in its turn via the felt drives the upper presser roller 1, the invention embraces also such a press, in which the upper as well as the lower roller 1 and 2., respectively, is positively driven.

What we claim is:

1. A press for dewatering a humid or a wet web, e.g. a paper web or another fibre web carried by a felt, and of the kind comprising two rollers rotating in the same direction and being situated one above the other, viz a presser roller and a driving roller situated therebelow,

said last mentioned roller adapted, via a presser roller situated between the presser roller and the driving roller and extending parallel to these rollers and having a diameter considerably smaller than the diameter of said two rollers, and an endless, porous wire or cloth which is difficult to compress, to transmit a driving moment to the upper presser roller, wherein the improvement comprises the fact that means are provided to run said cloth over the small presser roller throuh the press nip between the same and the upper presser roller and is adapted to run under tension about the small presser roller which serves also as a pulley for the cloth. I

2. A press as claimed in claim 1, wherein the run of the cloth leaving the press nip runs in contact along a amounts to about 180 or more.

4. A press as claimed in claim 2, wherein the cloth known per se encloses the driving roller with an angle which is at least 45-90 so as to give the system sufiicient moment transmission.

5. A press as claimed in claim 1, wherein the cloth is manufactured from metal wires or a synthetic material in the shape of either monofilament or multifilament or both, the mesh size not exceeding 1 millimeter.

6. A press as claimed in claim 1 having a further upper presser roller carried for rotation above the driving roller and being parallel to the same, wherein there is between the driving roller and each one of the two upper presser rollers arranged a small presser roller cooperating with the upper presser rollers in question and serving as a pulley for an endless, porous cloth which is difiicult to compress, and forming with each of their upper presser roller two press nips in their points of contact.

7. A press as claimed in claim 6, wherein there runs over the small rollers a common, endless, porous cloth which is difiicult to compress and which also encloses the greater part of the driving roller.

8. A press as claimed in claim 6, wherein there is between the smaller presser rollers, forming a press nip with each their upper presser roller, carried a pulley over which the fibre web runs for the removal of the felt from it so as to prevent a rewetting in a way known per se.

FOREIGN PATENTS 5/1961 Great Britain.

REUBEN FRIEDMAN, Primary Examiner T. A. GRANGER, Assistant Examiner US. Cl. X.R. 

